The broad objective of the proposed project is to develop a method for induction of specific immunologic tolerance against strongly immunogenic contact allergens by feeding or injecting structurally related but non-immunogenic and presumably unconjugated or weakly immunogenic simple chemical tolerogens. We shall use the following compounds: 1,2-dichloro-4-nitrobenzene (DCNB) and 1,4-dichloro-2, nitrobenzene (CNCB), both non-sensitizers; 1,3,5-trinitrobenzene (1,3,5 TNB) a weak sensitzer, and 1,2,4-trinitrobenzene (1,2,4 TNB) a rather potent sensitizer. Futhermore, the investigators, together with Inga Silberberg, M.D., will continue their work on the role of the Langerhans cell in cell-mediated reactions. This role is not limited to contact allergic reactions but extends also to cell-mediated reactions induced by other allergens (e.g., ferritin). BIBLIOGRAPHIC REFERENCES: Silberberg, I., Baer, R.L., Rosenthal, S.A., Thorbecke, G.J. and Berezowsky, V.: Dermal and intravascular Langerhans cells at sites of passively induced allergic contact sensitivity. Cellular Immunol. 18:435-453, 1975. Silverberg, I., Baer, R.L., Rosenthal, S.A., Thorbecke, G.J. and Berezowsky, V.: Langerhans cells in skin, lymphatic-like vessels and draining lymph nodes in allergic contact sensitivity. Clin. Res. 23:231A, 1975.